For an ideal gas system, which of the following thermodynamic processes definitively result in no ch — Thermodynamics and Thermochemistry Chemistry Question

💡 Solution & Explanation

The internal energy ($U$) of an ideal gas depends solely on its absolute temperature ($T$). (A) In an isothermal expansion, $\Delta T = 0$, meaning $\Delta U = 0$. (B) In adiabatic expansion, the gas does work at the expense of its internal energy, causing a temperature drop ($\Delta U < 0$). (C) Free expansion against vacuum means $w=0$. Since an ideal gas does not undergo cooling in free expansion, $\Delta T=0$ and $\Delta U=0$. (D) In a cyclic process, initial and final states are identical; since $U$ is a state function, $\oint dU = 0$.